Fear of anxiety symptoms (anxiety sensitivity) has been implicated in the etiology and maintenance of panic disorder, and has been shown to improve with cognitive-behavioral treatment. The impact of pharmacotherapy on anxiety sensitivity is less clear. We administered the Anxiety Sensitivity Index (ASI) during a 12-week randomized controlled trial investigating the relative efficacy of paroxetine, paroxetine plus sustained clonazepam, and paroxetine plus brief clonazepam for patients with panic disorder. We found a mean reduction in ASI scores of 9.6 points, which correlated with symptomatic improvement, and did not differ significantly between groups. Our data provides further evidence that pharmacotherapy leads to significant acute reductions in fears of anxiety symptoms in patients with panic disorder, albeit at levels that may be somewhat less than the changes associated with CBT. Implications of these findings are discussed relative to optimizing pharmacologic treatment of panic disorder.